Hammer-strikable, powder-actuated, fastener-driving tools are used commonly to drive fasteners, such as drive pins, into concrete, masonry, or steel structures. Such a tool derives its motive power from blank cartridges containing gunpowder.
Such tools are exemplified in Kostas U.S. Pat. No. 4,025,029, Brosius U.S. Pat. No. 4,252,259, Kopf U.S. Pat. No. 4,493,376, Hawkins U.S. Pat. No. 4,651,912, Gottlieb et al. U.S. Pat. No. 4,830,252, and Hawkins U.S. Pat. No. 4,890,778. Such a tool may have a tool body defining a handle, a breech block mounted within the tool body by means of screws received by the tool body, and a firing pin movable within the breech block over a range of firing pin movement. The firing pin is biased so as to be normally disposed in a dormant position at a back extreme of the range and is capable of being impelled to a firing position at a front extreme of the range when the firing pin or a structure connected to the firing pin is struck forcibly with a hammer.
Thus, when the firing pin causes a cartridge loaded into the tool to fire, a fastener is driven forcibly from a muzzle by means of a piston and a driving blade. Also, explosive forces are produced, which impart high stresses on the tool particularly where the tool body receives screws or other fasteners mounting the breech block within the tool body. As described below, this invention deals with such stresses in a novel, advantageous manner.